The present invention relates to a process for forming a film on a substrate having a field emitter by bias enhanced nucleation chemical vapor deposition.
FIGS. 1A through 1C illustrate a process flow for forming a diamond film on a silicon field emitter, which has characteristics of low work function, high chemical/physical stability, and high hardness. The diamond film is utilized for improving the performance of a silicon field emission device.
FIG. 1A shows a silicon substrate 10 having a silicon tip as a field emitter 12.
As shown in FIGS. 1B through 1C, a diamond thin film 20 is grown by microwave plasma chemical vapor deposition (MPCVD), electron cyclone resonance chemical vapor deposition (ECR-CVD), or laser ablation. Subsequently, a final diamond layer 30 depicted in FIG. 1C is formed.
However, it is difficult to etch a diamond layer with conventional semiconductor technology due to its high hardness and high chemical/physical stability. Therefore, conventional diamond layer formation methods cannot be used in field emission devices that contain conductive gate. electrodes.
In view of the above disadvantages, an object of the invention is to provide a process for forming a film on a substrate having a field emitter. Thus, a carbon-containing film such as diamond film can be selectively deposited on a silicon tip.
Another object of the invention is to maintain a high aseptic ratio of the diamond film.
Also, further another object of the invention is to form a field emitter having multiple-tips so as to improve performance of the field emission device.
The above objects are attained by providing a process for forming a film on a substrate having a (silicon) field emitter, said process comprising the steps of: (a) cleaning said substrate and said field emitter by hydrogen plasma to remove the impurities thereon; (b) forming a silicon carbide film over said field emitter; (c) applying a negative bias voltage of about 150 V to about 300 V to said substrate for increasing the nucleation sites of said silicon carbide film; and (d) stopping said negative bias voltage so as to grow a carbon-containing film from said silicon carbide film.
In an embodiment of said invention, the silicon carbide film in step (b) is formed by electron cyclone resonance chemical vapor deposition (ECR-CVD) using a mixture gas containing silicane and methane, wherein the process is performed at room temperature and with a microwave power of about 1000W.
The step (b) of the process of this invention can further comprise the step of applying a negative bias voltage of about 100 V to about 300 V to said substrate.
The carbon-containing film formed by the process of this invention can be a diamond film, diamond-like film, amorphous carbon film, or graphite-like film.